System for converting fuel and air into reformate and method for mounting such system

ABSTRACT

The invention relates to a system for converting fuel and air into reformate with a reformer ( 10 ) which has a reaction space ( 12 ), a nozzle ( 14 ) for supplying a fuel/air mixture to the reaction space ( 12 ), and a fuel feed ( 16 ) for supplying fuel to the nozzle ( 14 ). As claimed in the invention it is provided that in the air inlet area ( 18 ) of the nozzle ( 14 ) there are air guidance means ( 40 ) which impart a swirl to the inflowing air.

[0001] The invention relates to a system for converting fuel and airinto reformate with a reformer which has a reaction space, a nozzle forsupplying a fuel/air mixture to the reaction space, and a fuel feed forsupplying fuel to the nozzle. The invention furthermore relates to aprocess for installing one such system.

[0002] Generic systems are used to convert chemical energy intoelectrical energy. For this purpose fuel and air, preferably in the formof a fuel/air mixture, are supplied to the reformer. In the reformerthen conversion of the fuel with atmospheric oxygen takes place,preferably the process of partial oxidation being carried out.

[0003] The reformate which has been produced in this way is thensupplied to a fuel cell or a stack of fuel cells, electrical energybeing released by the controlled reaction of hydrogen, as a component ofthe reformate, and oxygen.

[0004] The reformer, as already mentioned, can be designed such that theprocess of partial oxidation is carried out to produce the reformate. Inthis case, when using diesel as the fuel it is especially useful tocarry out prior reactions before partial oxidation. In this waylong-chain diesel molecules can be converted into short-chain moleculeswith a “cold flame”; this ultimately promotes reformer operation. Ingeneral a gas mixture which is reacted to H₂ and CO is supplied to thereaction zone of the reformer. Another component of the reformate is N₂from the air, and depending on the air ratio and the temperature,optionally CO₂, H₂O and CH₄. In normal operation the fuel mass flow iscontrolled according to the required output, and the air mass flow isadjusted to an air ratio in the range of λ=0.4. The reforming reactioncan be monitored by different sensors, for example, temperature sensorsand gas sensors.

[0005] In addition to the process of partial oxidation, it is likewisepossible to carry out autothermal reforming. The process of partialoxidation, in contrast to autothermal reforming, is caused by the oxygenbeing supplied substoichiometrically. For example the mixture has an airratio of λ=0.4. Partial oxidation is exothermal so that unwanted heatingof the reformer can occur in a problematical manner. Furthermore,partial oxidation tends to intensify soot formation. To prevent sootformation, the air ratio λ can be chosen to be smaller. This is achievedsuch that some of the oxygen used for oxidation is made available bywater vapor. Since oxidation with water vapor proceeds endothermally, itis possible to adjust the ratio between the fuel, oxygen and water vaporsuch that overall heat is neither released nor consumed. The autothermalreforming achieved in this way therefore eliminates the problem of sootformation and undesirable overheating the reformer.

[0006] Likewise it is possible for further steps of gas treatment toproceed following oxidation in the reformer, and especiallymethanization can be connected downstream of partial oxidation.

[0007] A current fuel cell system is for example a PEM system (“protonexchange membrane”) which can typically be operated at operatingtemperatures between room temperature and roughly 100° C. Based on thelow operating temperatures, this type of fuel cell is often used formobile applications, for example in motor vehicles.

[0008] Furthermore, high temperature fuel cells are known, so-calledSOFC systems (“solid oxide fuel cell”). These systems work for examplein the temperature region of roughly 800° C., a solid electrolyte(“solid oxide”) being able to take over transport of oxygen ions. Theadvantage of these high temperature fuel cells over PEM systems consistsespecially in durability relative to mechanical and chemical loads.

[0009] One application for fuel cells in conjunction with genericsystems includes not only stationary applications, but also especiallyapplications in the motor vehicle domain, for example as “auxiliarypower units” (APU).

[0010] For reliable operation of the reformer it is important to supplythe fuel or fuel/air mixture in a suitable manner to the reaction spaceof the reformer. For example, good mixing of the fuel and air and a gooddistribution of the fuel/air mixture in the reaction space of thereformer are advantageous for the operation of the reformer. Within theframework of this disclosure, it is always a fuel-air mixture ifsubstances added or to be added to the reaction space of the reformerare addressed. The added substances are not limited however to themixture of fuel and air. But rather other substances can also be addedin addition, for example water vapor in the case of autothermalreforming. To this extent the concept of fuel/air mixture should beunderstood in this more general form.

[0011] The object of the invention is to make available a system forreaction of fuel and air into reformate which has advantageousproperties with respect to introducing the fuel/air mixture into thereaction space of the reformer.

[0012] This object is achieved with the features of the independentclaims.

[0013] Advantageous embodiments of the invention are given in thedependent claims.

[0014] The invention is based on the generic prior art in that there areair guidance means in the air inlet area which impart a swirl to theinflowing air. Within the framework of this disclosure the concept ofair inlet area should be understood very generally. On the one hand, forexample, a cylindrical part of the flow path can be meant by Venturinozzle. But the area outside the Venturi nozzle can also be called theair inlet area. What is intended in particular follows from the context.By swirling the air entering the nozzle, in the air entry area theatomization quality and thus the function of the reformer can be clearlyimproved. The reason for this is that the air speed is increased due tothe pronounced tangential motion component.

[0015] In this connection it can be considered especially advantageousif the air guidance means comprise an air-guiding device with swirlblades. One such air-guiding device as a separate component can beproduced independently of the nozzle and seated on it.

[0016] In this case it is provided that the swirl blades are located ona carrier mounted on the nozzle assembly, and that two swirl blades at atime together with the carrier and the nozzle assembly form a conicalchannel. The tangential air portion and thus the nozzle air swirl can beset depending on the angular position of these swirl blades to oneradial plane at a time. The swirl blades can be located roughly radiallyor tilted to the radii. The swirl blades can be made flat or curved inthe flow direction.

[0017] Likewise it is possible for the air-guiding device to have apot-shaped sleeve which is attached to the nozzle assembly with theaxial air holes formed in it and peripheral air holes formed in theperipheral wall. In this way it is possible to impart a defined swirl tothe air flowing into the nozzle.

[0018] In this connection it is possible for the peripheral air openingsto be holes which are formed almost tangentially to the peripheral wall.The tangential arrangement of the holes makes it possible to impart aswirl to the air without further aids.

[0019] Furthermore it can also be provided that on the peripheral airopenings there are air guide blades. It is therefore unnecessary todirectly impart the swirl through the peripheral air holes. Rather it isconceivable to allow the air to flow in through peripheral air holesmade in any way and then to impart the swirl by the air guide blades.

[0020] Furthermore, the system as claimed in the invention can befurther developed by the nozzle being a Venturi nozzle with an air inletarea and a diffusor area which extends downstream with respect to theair inlet area. One such Venturi nozzle causes a high axial air pressuregradient so that advantageously combustion air can be intaken and can bemixed with fuel in the diffusor area. In the air inlet area or in thearea in which the fuel is supplied to the nozzle, the air flowing intothe nozzle has a high speed and an accordingly low pressure. The highflow velocity of the air promotes absorption of the fuel by theinflowing air. As the fuel/air mixture subsequently flows through thediffusor area of the Venturi nozzle, a pressure recovery occurs so thatthe mixture can flow into the combustion space of the reformer withsufficient pressure. Furthermore, in the diffusor area advantageousmixing of fuel and air takes place. Thus an effective and economicalpossibility is created for delivering the fuel/air mixture into thereformer. The installation cost and production costs can be benefited bythe choice of different embodiments. For example, it is conceivable toform at least part of the diffusor area in one piece with the reformeror the reformer housing or the housing of the reaction space. But it isalso conceivable to make and use the nozzle as a whole independently ofthe reformer.

[0021] It can be advantageously provided for the opening angle of thediffusor area to be variable. Even if in the simplest case the diffusorarea has a uniform opening angle, it can be useful especially forlinking the diffusor part to the reaction space to provide a largeropening angle in the entry area into the combustion chamber. Thissupports the uniform distribution of the fuel/air mixture in thereaction space, while the opening angle of the part of the diffusor areawhich is further upstream can be optimized with respect to the flowbehavior in this area.

[0022] The system as claimed in the invention is furthermore developedin an especially advantageous manner by the liquid fuel being suppliedto the Venturi nozzle in the vicinity of the air inlet area through aneedle. This fuel needle is supplied with fuel via a fuel line. Based onthe high flow velocity of the inflowing air, the fuel emerging from thefuel needle almost unpressurized is pulled into filaments which thenbreak down into droplets. The high air speeds which are necessary forgood atomization in the air inlet area can be achieved there as a resultof the advantageous pressure recovery of the diffusor.

[0023] Likewise, the system as claimed in the invention can be developedin an especially advantageous manner by the fuel feed comprising a pipeand a binary fuel nozzle so that a fuel/air mixture is supplied to theVenturi nozzle. Therefore, before the fuel enters the Venturi nozzlemixing of the fuel with the air is already taking place; this can beadvantageous for reliable mixing.

[0024] In this connection it can be provided that the binary nozzle isanother Venturi nozzle. Within the Venturi nozzle which is used withinthe framework of the invention and which can also be called a Venturitube, there is a smaller Venturi nozzle with a fuel needle located init. In the smaller Venturi nozzle, emergence of the fuel from the fuelneedle and premixing take place. The fuel/air mixture then enters theVenturi tube, i.e. the Venturi nozzle as claimed in the invention, andit further mixed there in order to finally enter the reaction space.

[0025] It can be especially preferred that there are means so thatsecondary air can flow into the reaction space. The air entering throughthe Venturi nozzle into the reaction space, i.e. the air present in thefuel/air mixture, can be called primary air in this connection. Thesecondary air is advantageously conveyed through the secondary airopenings in the housing of the reaction space. The division of the airinto primary air and secondary air can be useful for preparing a rich,easily ignited mixture at the outlet of the nozzle. This is especiallyuseful in the starting process of the system, since here the reformerworks advantageously as a type of burner.

[0026] The system as claimed in the invention is furthermore especiallyadvantageously developed in that the fuel feed encompasses a fuel needleand that for the ratio of the inside diameter d_(i) to the outsidediameter da of the fuel needle the following applies:

0.7≦d_(i)/d_(a)<1.

[0027] The fuel needle is therefore made extremely thin-walled so thatat a given fuel throughput, i.e. a given inside diameter, an outsidediameter as small as possible is ensured. This ultimately leads to anespecially small flow barrier due to the presence of the needle. Theindicated tolerance range is chosen such that the needle can be producedwithout major difficulty, the principle underlying this invention beingbetter satisfied, the more the ratio of the inside diameter to outsidediameter of the fuel needle approaches a value of 1.

[0028] The system as claimed in the invention is developed especiallyadvantageously in that the Venturi nozzle is axially symmetrical and thefuel needle is axially aligned. The axial alignment of the fuel needlemakes available to it a low flow resistance for the combustion air. Butif the effort is made to introduce the fuel at a certain angle into theflow area of the Venturi nozzle, it is likewise possible to tilt thefuel needle against the axis of the Venturi nozzle. In this case theindicated useful ratio between the inside diameter and the outsidediameter contributes to minimization of the flow resistance.

[0029] Furthermore, it can be useful for the exit plane of the liquidfuel from the fuel needle to run perpendicularly to the flow directionof the liquid fuel through the fuel needle. In this way axiallysymmetrical emergence of the fuel from the fuel needle results, ignoringgravity.

[0030] But it can also be useful for the exit plane of the liquid fuelfrom the fuel needle to run obliquely to the flow direction of theliquid fuel through the fuel needle. In this way a preferentialdirection upon emergence of the fuel from the fuel needle can beimplemented without the fuel needle tilting overall against the axis ofthe Venturi nozzle. Due to the oblique cut of the fuel needle in theexit area therefore an increase of the flow resistance as a result ofthe tilted fuel needle can be avoided, but emergence of the fuel fromthe fuel needle pointed for example against the force of gravity isstill possible.

[0031] Furthermore, it is possible for the exit opening of the fuelneedle to be provided with tips and/or to be crenelated. This makes itpossible for the fuel to be introduced into the fuel chamber with greatradial extension; this cannot be achieved in the optimum manner inopenings without a structure on the edge of the exit due to constrictioneffects, among others.

[0032] The system as claimed in the invention is furthermore preferablydeveloped in that the air inlet area has an essentially cylindrical partwhich has a transition to the diffusor area, that the exit opening ofthe fuel needle is located in the cylindrical part and that there is anaxial distance between the exit opening of the fuel needle and thetransition. This ensures that the liquid fuel which has emerged from theexit opening of the fuel needle is still transported together with theinflowing air over a certain distance through a region of high flowvelocity. This ensures especially good atomization. In most cases itwill be a good idea to place the exit from the fuel needle at the startof the cylindrical part of the air inlet area of the Venturi nozzle sothat essentially the entire cylindrical area is available for gooddistribution of the atomized fuel in the rapidly flowing combustion air.

[0033] Furthermore, the system as claimed in the invention isadvantageously developed by its being designed with respect to at leastone installation possibility of the reformer in a motor vehicle, so thatthe opening of the fuel needle is located above the axis of the Venturinozzle. This circumstance makes it possible to arrange the fuel needleparallel to the axis of the Venturi nozzle and at the same time tocounteract the effect of gravity. If the installation position of thefuel needle is chosen with respect to the axis of the Venturi nozzle fora possible installation position of the reformer such that it is pushedaway from the axis radially upward and then in the peripheral direction,two installation positions of the reformer can be allowed, for the twoinstallation positions favorable equalization of the force of gravitytaking place by the location of the opening above the axis of theVenturi nozzle.

[0034] Furthermore, the system as claimed in the invention can bedeveloped by the nozzle consisting of ceramic material and by the airguidance means being made in one piece with the nozzle. In this way anozzle which can be economically produced is made, available. Theceramic material can be easily machined, numerous variations beingpossible with respect to shaping. In particular the air guidance meanswhich impart a swirl to the air outside the air inlet area can be madein one piece with the nozzle. As a result of using a ceramic, there isthe additional advantage that the area of the nozzle around the fuelneedle located in the nozzle does not assume overly high temperatures sothat ignition of the amounts of fuel which may be emerging form thenozzle cannot occur. The one-piece execution of the air guidance meansmakes it possible to easily adhere to tolerances since miscalibration ofthe air guidance means is no longer possible when the reformer isassembled.

[0035] The invention is furthermore advantageously developed in that thenozzle has means for holding a glow pin. The positioning of the glow pinwith respect to the nozzle is an important parameter with respect togood starting behavior of the reformer. In heaters of the prior art, theglow pin was generally held by the reformer housing so that in this waypositioning fluctuations with respect to the nozzle could occur. Thesetolerances can be eliminated by the property of the nozzle as claimed inthe invention that the nozzle itself has means for holding the glow pin.The glow pin always has the same position relative to the nozzle.

[0036] Furthermore, the nozzle as claimed in the invention isadvantageously developed by the nozzle having at least partially anessentially cylindrical shape and by the air guidance means formingchannels which are offset with respect to the radial directions. The airflowing in perpendicular to the axis of the nozzle is therefore notradially supplied, but with an offset. This offset determines the swirlwhich is imparted to the air, thus the flow behavior and ultimately alsothe properties and the quality of the combustion.

[0037] It is especially useful for the air guidance means to haveessentially triangular base surfaces, the comers being rounded. In thisway the channel offset can be easily implemented. The rounding of thecomers is advantageous for uniform flow behavior.

[0038] In another preferred embodiment of this invention it is providedthat the means for holding the glow pin are made as a hole which runsslanted to the cylinder axis. The glow pin must then be introducedsimply into the hole for suitable positioning. A stop on the glow pinand/or within the hole provides for the glow pin to be guided into itsoptimum position with respect to the nozzle.

[0039] The nozzle as claimed in the invention is developed especiallyadvantageously in that an at least essentially cylindrical part of thenozzle has an essentially cylindrical shoulder with an enlarged diameterand that the means of holding the glow pin are made as a hole whichpenetrates the shoulder and which runs slanted to the cylinder axis. Inthis way the glow pin can be held in the area so that it influences theflow behavior of the inflowing fuel-air mixture as little as possible.By means of the cylindrical shoulder which has a larger diameter thanthe remaining nozzle body, this can be easily implemented.

[0040] Likewise, it is provided in an especially advantageous mannerthat an at least essentially cylindrical part of the nozzle has anessentially cylindrical shoulder with an enlarged diameter and that thecylindrical shoulder has recesses for holding the mounting pins. Thesemounting pins can be for example permanently mounted on the heat shieldof the reformer. The relative positioning of the nozzle is fixed in thisway by the recesses in the shoulder and the position of the mountingpins. Thus mounting is especially easily possible with only smalltolerances.

[0041] In another preferred embodiment the system as claimed in theinvention can be developed such that the reformer, the nozzle and thefuel feed are located on one axis, that there are means for holding thenozzle and the fuel feed, that there are at least two axially alignedmounting pins which are mounted on the reformer, that the nozzle and thefuel feed comprise positioning means which interact with the mountingpins, that the means for holding the components interact with themounting pins and that the reformer, the nozzle, the fuel feed and themeans for holding the components are located axially in succession. Inthis way all positions of the components are oriented to the mountingpins so that narrow tolerances can be maintained. The fuel needle ispositioned extremely accurately with respect to the nozzle. Furthermorethe positioning of the glow pin which is required for starting behavioris dictated by the positions of the mounting pins. Ultimately a stablestructure which ensures reformer operation with high quality isobtained.

[0042] The device as claimed in the invention is advantageouslydeveloped in that the means for holding the components are made as aspring which is held on the mounting pin by clamp disks. Attachment withone such spring has the advantage that mechanical stresses, especiallyas a result of temperature effects, can be equalized. In systems of theprior art undesirably high forces could act on the reformer and on anoptional heat shield of the reformer due the mechanical stresses, bywhich it was ultimately deformed.

[0043] Furthermore, it is advantageously provided that the mounting pinsare welded onto the reformer. In this way the mounting pins are securelyconnected to the reformer in a defined position with respect to thelatter.

[0044] Furthermore, it is especially preferred that between the nozzleand the reformer there is a seal. It is used both for thermal insulationand also for matching the nozzle to the heat shield of the reformer.

[0045] It is furthermore advantageously provided that the seal has atleast one mica layer facing the reformer and at least one graphite layerfacing the nozzle. This makes available the indicated advantageousproperties of the seal in an especially reliable manner.

[0046] It can furthermore be advantageously provided that the fuel feedhas a metal knit. This is used to break down bubbles in the fuel.Furthermore, in this way a counterpressure for a damper which isoptionally located on the fuel line is made available.

[0047] The invention furthermore relates to a process for installing asystem for conversion of fuel and air into reformate, there being atleast two mounting pins, in which one nozzle is guided in the axialdirection onto the mounting pins, a fuel feed is guided in the axialdirection onto the mounting pins, and means for holding the componentsare guided in the axial direction onto the mounting pins. One suchprocess can be implemented especially easily since all components aresupplied in the axial direction. In particular the process can beautomated since large numbers can be produced within a short time.

[0048] The process is furthermore advantageously developed in thatbefore guiding the nozzle onto the mounting pins a seal is guided in theaxial direction onto the mounting pins. The device provided with theabove described advantages, with a seal can thus likewise be integratedinto the process, especially since the seal is also guided in the axialdirection onto the mounting pins.

[0049] The process as claimed in the invention is furthermoreadvantageous in that the means for holding the components is a springand that the spring is guided force-controlled onto the mounting pinswith the interaction of clamp disks which fix the spring in its endposition.

[0050] Thus, uniform prerequisites can be established with respect toheat and temperature properties of the structure within one series.Imparted by the spring force, tolerances as a result of differentheating of the components, different final temperatures of componentsand different coefficients of temperature expansion can be equalized.

[0051] The invention is based on the finding that it entails majoradvantages to use a Venturi nozzle to introduce the fuel/air mixtureinto the reformer. A Venturi nozzle offers for example the possibilityof liquid fuel being taken up especially efficiently in areas of highflow velocity into the inflowing air, subsequently a sufficient pressurebuild-up being ensured to introduce the fuel/air mixture into areformer. A Venturi nozzle can be economically produced in numerousembodiments. Furthermore, installation processes for the systems asclaimed in the invention are especially efficient.

[0052] The invention is explained by way of example with reference tothe attached drawings using preferred embodiments.

[0053]FIG. 1 shows a schematic block diagram of a system in which thisinvention can be used;

[0054]FIG. 2 shows a schematic sectional view of one embodiment of thesystem as claimed in the invention;

[0055]FIG. 3 shows a schematic sectional view of another embodiment of asystem as claimed in the invention;

[0056]FIG. 4 shows a diagram in explanation of the axial pressurebehavior in the Venturi nozzle;

[0057]FIG. 5 shows a schematic sectional view of another embodiment of asystem as claimed in the invention;

[0058]FIG. 6 shows a perspective of a carrier with an air-guiding devicefor use in a system as claimed in the invention;

[0059]FIG. 7 shows schematic sectional view of another embodiment of thesystem as claimed in the invention;

[0060]FIG. 8 shows a schematic sectional view along the cross sectionalplane identified by A-A in FIG. 7;

[0061]FIG. 9 shows a schematic sectional view, corresponding to thesection as shown in FIG. 8, of another embodiment of an air-guidingdevice;

[0062]FIG. 10 shows a schematic sectional view of another embodiment ofthe system as claimed in the invention;

[0063]FIG. 11 shows a schematic sectional view along the planeidentified by B-B in FIG. 10;

[0064]FIG. 12 shows a fuel needle with a first exit opening for use inthe system as claimed in the invention;

[0065]FIG. 13 shows a fuel needle with a second exit opening for use inthe system as claimed in the invention;

[0066]FIG. 14 shows a fuel needle with a third exit opening for use inthe system as claimed in the invention;

[0067]FIG. 15 shows a partially cut side view of the embodiment of anozzle for use in the system as claimed in the invention;

[0068]FIG. 16 shows an overhead view of the air inlet area of a nozzlefor use in a system as claimed in the invention; and

[0069]FIG. 17 shows a schematic sectional view of another embodiment ofthe system as claimed in the invention.

[0070] In the following description of the drawings the same referencenumbers label the same or comparable components.

[0071]FIG. 1 shows a schematic block diagram of a system in which thisinvention can be used. Fuel 216 is supplied to a reformer 214 via a pump240. Furthermore, air 218 is supplied to the reformer 214 via a fan 242.The reformate 220 produced in the reformer 214 travels via a valve means222 to the anode 224 of a fuel cell 212. The cathode 230 of the fuelcell 212 is supplied with cathode feed air 228 via a fan 226. The fuelcell 212 produces electrical energy 210. The anode exhaust gas 234 andthe cathode exhaust air 236 are supplied to the burner 232. Likewisereformate can be supplied to the burner 232 via the valve means 222. Thethermal energy produced in the burner 232 can be supplied in a heatexchanger 238 to the cathode feed air 228 so that it is preheated.Exhaust gas 250 flows out of the heat exchanger 238.

[0072] The system shown in conjunction with the figures described belowcan be used to supply a fuel/air mixture to the reformer 214.

[0073]FIG. 2 shows a schematic sectional view of one embodiment of thesystem as claimed in the invention. The system comprises a reformer 10with a reaction space 12. A Venturi nozzle 14 is connected to thereformer 10. The nozzle has an air inlet area 18 and a diffusor 20 witha cross section which increases in the direction to the reformer 10.Within the Venturi nozzle 14 in the vicinity of the air inlet area 18there is a fuel feed 16. It comprises a pipe 24 for feed of fuel and abinary nozzle 26. The binary nozzle 26 is provided with an opening 80into which air 82 can flow. The air is mixed within the binary nozzle 26with fuel supplied by the pipe 24. From the downstream opening of thebinary nozzle 26 then a fuel/air mixture can emerge which is entrainedby the air 82 which enters the air inlet area 18 of the Venturi nozzle14. The fuel/air mixture mixes with the air 82 which has flowed into theair inlet area 18 of the Venturi nozzle 14, and the resulting fuel/airmixture travels via the diffusor 20 into the reaction space 12 of thereformer 10. Furthermore, it is possible to provide an opening 30 to thereaction space 12 of the reformer 10 through which secondary air 82 canenter the reaction space 12.

[0074]FIG. 3 shows a schematic sectional view of another embodiment ofthe system as claimed in the invention. The fuel feed 16 in the systemshown in FIG. 3 is different from in the system shown in FIG. 2. Thefuel is first supplied in turn via a pipe 24, but then travels intoanother Venturi nozzle 28 which is much smaller than the Venturi nozzle14. In the Venturi nozzle 28 the liquid fuel is picked up and atomizedby the air 82 which is flowing past the exit opening of the pipe 24 athigh speed. The resulting fuel/air mixture is then entrained by the air82 which flows in the air inlet area 18 of the Venturi nozzle 14 so thatit can mix with it.

[0075]FIG. 4 shows a diagram in explanation of the axial pressuredistribution in a Venturi nozzle. The pressure difference Δp between thepressure at a certain coordinate 1 and the pressure in the reactionspace 12 (see FIGS. 2 and 3) is plotted. The air 82 is generally fedinto the air inlet region 18 of the Venturi nozzle 14 by a fan (notshown), this air being made available with only a low overpressure. As aresult of the speed increase of the inflowing air the pressure drops toa minimum value. As the air continues to flow through the diffusor ofthe Venturi nozzle, the flow velocity decreases again and the pressureincreases gradually to the reaction chamber pressure.

[0076]FIG. 5 shows a schematic sectional view of another embodiment of asystem as claimed in the invention. The system comprises a Venturinozzle 14 with a nozzle assembly 44. Furthermore there is a fuel feed 72for supplying liquid fuel to the nozzle 14. The fuel is supplied to theair inflow area 92 via the fuel exit 84 of the fuel needle 22, thereentrained by the inflowing air and then travels as a fuel/air mixture tothe reaction space 12 of the reformer 10 via the diffusor 20. The nozzleassembly 44 is connected downstream of an air-guiding device 42 whichimpresses a swirl on the air flowing into the Venturi nozzle 14. Theair-guiding device 42 is made as a carrier 46 which is located oppositethe end face 90 of the nozzle assembly 44 with a distance, and is forexample circular. It forms an annular gap 86 together with the end face90 of the nozzle assembly 44. On the carrier 46 there are swirl blades88 which are pointed against the end face 90 of the nozzle assembly 44and adjoin it in the assembly position.

[0077]FIG. 6 shows a perspective view of an air-guiding device 42 foruse in a system as claimed in the invention. The swirl blades 88 arearranged offset on a carrier 46 with respect to the radii of thecircular arrangement in order to produce a tangential flow component.Two swirl blades 88 at a time together with the carrier 46 and thenozzle assembly 44 form a conical channel 48.

[0078]FIG. 7 shows a schematic cross sectional view of anotherembodiment of a system as claimed in the invention. This embodiment ofthe system as claimed in the invention differs from that shown in FIG. 5in that the air-guiding device 42 is made as a pot-shaped sleeve 96. Thesleeve 96 in its bottom has axial holes 94, and in the peripheral wall100 of the sleeve 96 tangential holes 98 are formed. The sleeve 96 isattached to the nozzle assembly of the Venturi nozzle 14, for example byslipping it on or by some other form of positive, nonpositive ormaterial connection. The axial holes 94 and the tangential holes 98 arematched to one another such that a defined swirl is imparted to theinflowing air. FIG. 8 shows a schematic sectional view along the crosssectional plane identified by A-A in FIG. 7. A sample arrangement of theaxial holes 94 and the tangential holes 98 in the sleeve 96 is shown. Byvarying the number of openings or holes 94, 98 and the size andarrangement the swirl of the air flow can be adjusted if necessary.

[0079]FIG. 9 shows a schematic sectional view, corresponding to FIG. 8,of another embodiment of an air-guiding device. The sleeve 96 shown herein its peripheral wall 100 has air holes 102 which are bordered towardsthe center of the sleeve 96 by an air guide blade 104 which is assignedto the respective air opening 102. A tangential flow component isimpressed on the inflowing air by the air guide blades 104.

[0080]FIG. 10 shows a schematic sectional view of another embodiment ofa system as claimed in the invention. The function and properties of thecomponents shown result from the preceding description withconsideration of the reference numbers. The representation is highlyschematic so that important components of the system can be detected. Inthe cylindrical part 38 of the Venturi nozzle 14 there is a fuel needle22 for supplying fuel. On the one hand it is a good idea to arrange thefuel needle 22 in exactly this narrowed cylindrical part 38 of theVenturi nozzle 14, since the combustion air 82 flowing with high flowvelocity promotes atomization of the fuel. On the other hand, the fuelneedle 22 however also represents a flow barrier to the inflowingcombustion air 82. This is a basic problem which is solved by thefeatures described below in conjunction with the system as claimed inthe invention. Line B-B identifies a radial cutting plane to whichreference is made in the following description.

[0081]FIG. 11 shows a sectional view along the plane identified in FIG.10 with B-B. It can be recognized how this invention solves the problemdescribed in conjunction with FIG. 10. By choosing the ratio between theinside diameter d_(i) and the outside diameter da of the fuel needle 22to be as near a value of 1 as possible, the fuel needle 22 represents aminimum flow resistance for the inflowing combustion air in the Venturinozzle 14.

[0082]FIG. 12 shows a fuel needle 22 with a first exit opening for usein a system as claimed in the invention. In this case the exit plane 32of the fuel 106 from the fuel needle 22 is perpendicular to the mainflow direction of the fuel 106. This results in constriction of the fuel106 outside the fuel needle 22; among others, this can bedisadvantageous with respect to the uniform distribution of the fuel 106in the Venturi nozzle and ultimately in the combustion chamber.

[0083]FIG. 13 shows a fuel needle 22 with a second outlet opening foruse in a system as claimed in the invention. Here the exit opening ofthe fuel needle 22 has crenelations 36. These crenelations 36concentrate emerging fuel 106 in certain areas and ultimately the resultis that the fuel 106 is distributed almost homogeneously over the entireflow cross section available to it.

[0084]FIG. 14 shows a fuel needle 22 with a third exit opening for usein a system as claimed in the invention. Here the fuel needle 22 with abevelled opening 34 can be recognized. The latter imparts to theoutflowing fuel 106 a preferential direction so that for example theeffect of the force of gravity can be counteracted.

[0085] The special embodiments of the fuel needles which are describedwithin the framework of this disclosure can be combined in a manneradvantageous to the invention. For example, it is conceivable for aslanted exit plane to be combined with a crenelated structure.

[0086]FIG. 15 shows a partially cutaway side view of one embodiment of anozzle 14 for use in a system as claimed in the invention. The Venturinozzle 14 is made of ceramic material; this simplifies the production ofthe nozzle 14 compared to metal nozzles. In the air inlet area 18 thereare air guidance means 40. They are made in one piece with the nozzle14. In particular, they are also made of ceramic material. The air guideelements 40 are aligned such that a swirl is imparted to the suppliedair; this is detailed below with reference to FIG. 16. The Venturinozzle 14 is furthermore provided with a hole 62. A glow pin 64 can beinserted into this hole 62 and is used to ignite the fuel/air mixtureentering the reaction space which is not shown in FIG. 15. Inparticular, when the system as claimed in the invention starts, thereformer works in the manner of a burner so that initial ignition of thefuel/air mixture can be necessary. It is advantageous in the arrangementof the glow pin 64 in a hole 62 of the nozzle 14 that the positioning ofthe glow pin 64 is fixed with respect to the nozzle 14. Therefore thepositioning of the glow pin 64 does not especially depend on any othercomponents. In this way very small tolerances can be maintained withrespect to the installation location of the glow pin 64. The hole 62advantageously penetrates the cylindrical shoulder 66 of the nozzle 14with an increased radius. This has the advantage that the flow behaviorof the nozzle 14 is influenced only little by the hole 62 or by the glowpin 64 which is located in the hole 62.

[0087]FIG. 16 shows an overhead view of the air inlet area 18 of anozzle 14 for use in the system as claimed in the invention. Onepossible configuration of the air inlet area 18 by the air guideelements 40 is shown. The air guide elements 40 form channels 48 for theinflowing air. These channels 48 are positioned with respect to theradii of the structure which is located essentially on one axis suchthat there is an offset. Air flowing in from the outside undergoes aswirl; this entails advantageous properties with respect to atomizationof the fuel emerging from the fuel needle. Furthermore, in thisrepresentation the arrangement of the opening 62 for holding the glowpin can be recognized. The glow pin penetrates an essentiallycylindrical shoulder 66. The shoulder 66 is furthermore provided withrecesses 68. These recesses 68 define the installation position of thenozzle 14; this is detailed below with respect to FIG. 17.

[0088]FIG. 17 shows a schematic cross sectional view of anotherembodiment of a system as claimed in the invention. The end of thereformer 10 facing the nozzle 14 is shown. The reformer 10 is borderedby the heat shield 108. On this heat shield 108 there are two mountingpins 80 in this sample embodiment. These mounting pins 70 can be weldedto the heat shield 108 or the reformer 10. The mounting pins 70 definethe positioning of the other components described below. First of all,there is a seal 78 which preferably consists of a mica layer and agraphite layer, the mica layer being turned toward the reformer 10 andthe graphite layer being turned toward the nozzle 14. A ceramic nozzle14 follows which sits with its recesses 88 shown in FIG. 16 on themounting pins 70. A fuel feed 72 which is connected to the fuel needle22 is seated on the nozzle 14. This fuel feed 72 is likewise positionedby the mounting pins 70. The fuel feed 72 is supplied with fuel by thefuel line 110 in which the fuel sensor 112 is located. The fuel feed 72is followed by a spring 74 which is likewise seated on the mounting pins70. The spring 74 is held by clamping disks 76 which sit immovably onthe mounting pins 70. The spring 74 is shown in the tensioned state inwhich the legs of the spring 74 are for example parallel to theinterposed disk. In the released state of the spring 74 the legs of thespring 74 are bent upward in the direction to the interposed disk. Aglow pin (not shown) is positioned in agreement with the embodiment of anozzle 14 shown in FIG. 15 by it and is held by a wire spring (notshown) which is supported on the nozzle 14.

[0089] The fuel feed 72 and thus the fuel needle 22 are automaticallyaligned with respect to the nozzle 14 in this way. Therefore only twocomponents are involved which influence the fuel feed and the mixing ofthe fuel with combustion air so that very low tolerances can bemaintained; this moreover is possible by the type of installation on themounting pins 70. Likewise the glow pin can be positioned exactly withrespect to the nozzle 14 and the reformer 10.

[0090] The production of the structure shown in FIG. 17 can be fullyautomated. In particular, the installation direction is uniformly axialso that only “threading” of the parts must be carried out. The seal 78makes available thermal insulation, coupling of the nozzle ceramic 14 tothe metal of the heat shield 108 and tolerance equalization. Thestructure can be advantageously mounted by power-controlled pressing ofthe clamp disks 76 onto the mounting pins 70 so that with respect to theheat and temperature properties of the structure uniform prerequisitescan be established. Imparted by the spring force, the tolerances as aresult of different heating of the components, different finaltemperatures of the components and different coefficients of temperatureexpansion can be equalized.

[0091] The features disclosed in the specification above, in thedrawings and in the claims can be important both individually and alsoin any combination for the implementation of the invention.

[0092] Reference number list

[0093]10 reformer

[0094]12 reaction space

[0095]14 Venturi nozzle

[0096]16 fuel feed

[0097]18 air inlet area

[0098]20 diffusor area

[0099]22 fuel needle

[0100]24 pipe

[0101]26 binary nozzle

[0102]28 Venturi nozzle

[0103]30 secondary air opening

[0104]32 exit opening

[0105]34 exit opening

[0106]36 crenelations

[0107]38 cylindrical part

[0108]40 air guidance means

[0109]42 air-guiding device

[0110]44 nozzle assembly

[0111]46 carrier

[0112]48 channel

[0113]62 hole

[0114]64 glow pin

[0115]66 cylindrical shoulder

[0116]68 recess

[0117]70 mounting pin

[0118]72 fuel feed

[0119]74 spring

[0120]76 clamp disk

[0121]78 seal

[0122]80 opening

[0123]82 air

[0124]84 fuel exit

[0125]86 annular gap

[0126]88 swirl blade

[0127]90 end face

[0128]92 air inflow channel

[0129]94 axial hole

[0130]96 sleeve

[0131]98 tangential hole

[0132]100 peripheral wall

[0133]102 air opening

[0134]104 air guide blade

[0135]106 fuel

[0136]108 heat shield

[0137]110 fuel line

[0138]112 fuel sensor

[0139]210 electric power

[0140]212 fuel cell

[0141]214 reformer

[0142]216 fuel

[0143]218 air

[0144]220 reformate

[0145]222 valve means

[0146]224 anode

[0147]226 fan

[0148]228 cathode feed air

[0149]230 cathode

[0150]232 burner

[0151]234 anode exhaust gas

[0152]236 cathode exhaust air

[0153]238 heat exchanger

[0154]240 pump

[0155]242 fan

[0156]250 exhaust gas

1. System for converting fuel and air into reformate with a reformer(10) which has a reaction space (12), a nozzle (14) for supplying afuel/air mixture to the reaction space (12), and a fuel feed (16) forsupplying fuel to the nozzle (14), characterized in that in the airinlet area (18) of the nozzle (14) there are air guidance means (40)which impart a swirl to the inflowing air.
 2. System as claimed in claim1, wherein the air guidance means (40) comprise an air-guiding device(42) with swirl blades.
 3. System as claimed in claim 2, wherein theswirl blades (88) are located on a carrier (46) mounted on the nozzleassembly (44) and wherein two swirl blades at a time (88) together withthe carrier (46) and the nozzle assembly (44) form a conical channel. 4.System as claimed in claim 2 or 3, wherein the air-guiding device (42)has a pot-shaped sleeve (96) which is attached to the nozzle assembly(44) with the axial air holes (94) formed in it and peripheral air holes(98, 102) formed in the peripheral wall (100).
 5. System as claimed inclaim 4, wherein the peripheral air holes (8) are holes which are formedalmost tangentially to the peripheral wall (100).
 6. System as claimedin claim 4 or 5, wherein there are air guide blades (104) on theperipheral air holes (102).
 7. System as claimed in one of the precedingclaims, wherein the nozzle (14) is a Venturi nozzle with an air inletarea (18) and a diffusor area (20) which extends downstream with respectto the air inlet area (18).
 8. System as claimed in claim 7, wherein theopening angle of the diffusor area (20) is variable.
 9. System asclaimed in claim 7 or 8, wherein the Venturi nozzle (14) is suppliedwith liquid fuel in the vicinity of the air inlet area (18) by a needle(22).
 10. System as claimed in one of the preceding claims, wherein thefuel feed (16) comprises a pipe (24) and a binary nozzle (26, 28) sothat the Venturi nozzle (14) is supplied with a fuel/air mixture. 11.System as claimed in claim 10, wherein the binary nozzle is anotherVenturi nozzle (28).
 12. System as claimed in one of the precedingclaims, wherein there are means (30) so that secondary air can flow intothe reaction space (12).
 13. System as claimed in one of the precedingclaims, wherein the fuel feed (16) comprises a fuel needle (22) andwherein for the ratio of the inside diameter d_(i) to the outsidediameter d_(a) of the fuel needle the following applies:0.7<d_(i)/d_(a)<1
 14. System as claimed in one of the preceding claims,wherein the Venturi nozzle (14) is axially symmetrical and wherein thefuel needle (22) is aligned axially.
 15. System as claimed in one of thepreceding claims, wherein the exit plane (32) of the liquid fuel runsfrom the fuel needle (22) perpendicularly to the flow direction of theliquid fuel through the fuel needle (22).
 16. System as claimed in oneof claims 1 to 8, wherein the exit plane (34) of the liquid fuel runsfrom the fuel needle (22) obliquely to the flow direction of the liquidfuel through the fuel needle (22).
 17. System as claimed in one of thepreceding claims, wherein the outlet opening of the fuel needle (22) isprovided with tips and/or crenelations (36).
 18. System as claimed inone of the preceding claims, wherein the air inlet area (18) has anessentially cylindrical part (38) which has a transition to the diffusorarea (20), wherein the exit opening of the fuel needle (22) is locatedin the cylindrical part (38) and wherein there is an axial distancebetween the exit opening of the fuel needle (22) and the transition. 19.System as claimed in one of the preceding claims, wherein it is designedwith respect to at least one installation possibility of the reformer(10) in a motor vehicle, so that the opening of the fuel needle (22) islocated above the axis of the Venturi nozzle (14).
 20. System as claimedin one of the preceding claims, wherein—the nozzle (14) consists ofceramic material and the air guidance means (40) is made in one piecewith the nozzle (14).
 21. System as claimed in one of the precedingclaims, wherein the nozzle (14) has means for holding a glow pin (64).22. System as claimed in one of the preceding claims, wherein—the nozzle(14) has an at least partially essentially cylindrical shape and the airguidance means (40) form channels which are offset with respect to theradial directions.
 23. System as claimed in one of the preceding claims,wherein the air guidance means (40) have essentially triangular basesurfaces, the comers being rounded.
 24. System as claimed in one of thepreceding claims, wherein the means for holding the glow pin (64) aremade as a hole (62) which runs slanted to the cylinder axis.
 25. Systemas claimed in one of the preceding claims, wherein an at leastessentially cylindrical part of the nozzle (14) has an essentiallycylindrical shoulder (66) with an enlarged diameter and wherein themeans of holding the glow pin (64) are made as a hole (62) whichpenetrates the shoulder and which runs slanted to the cylinder axis. 26.System as claimed in one of the preceding claims, wherein—an at leastessentially cylindrical part of the nozzle (14) has an essentiallycylindrical shoulder (66) with an enlarged diameter and wherein thecylindrical shoulder (66) has recesses (68) for holding the mountingpins (70).
 27. System as claimed in one of the preceding claims, whereinthe reformer (10), the nozzle (14) and the fuel feed (72) are located onone axis, wherein there are means (74) for holding the nozzle (14) andthe fuel feed (72), wherein there are at least two axially alignedmounting pins (70) which are mounted on the reformer (10), wherein thenozzle (14) and the fuel feed (72) comprise positioning means whichinteract with the mounting pins (70), wherein the means (74) for holdingthe components interact with the mounting pins (70), and wherein thereformer (10), the nozzle (14), the fuel feed (72) and the means (74)for holding the components are located axially in succession.
 28. Systemas claimed in claim 27, wherein the means for holding the components aremade as a spring (74) which is held on the mounting pins (70) by clampdisks (76).
 29. System as claimed in claim 27 or 28, wherein themounting pins (70) are welded to the reformer (10).
 30. System asclaimed in one of the preceding claims, wherein there is a seal (78)between the nozzle (14) and the reformer (10).
 31. System as claimed inclaim 30, wherein the seal (78) has at least one mica layer facing thereformer (10) and at least one graphite layer facing the nozzle (14).32. System as claimed in one of the preceding claims, wherein the fuelfeed (72) has a metal knit.
 33. Process for installation of a system forconversion of fuel and air into reformate, there being at least twomounting pins (70), for which one nozzle (14) is guided in the axialdirection onto the mounting pins (70), a fuel feed (72) is guided in theaxial direction onto the mounting pins (70), and means (74) for holdingthe components are guided in the axial direction onto the mounting pins(70).
 34. Process as claimed in claim 33, wherein before guiding thenozzle (14) on the mounting pins (70) a seal (78) is guided in the axialdirection onto the mounting pins (70).
 35. Process as claimed in claim33 or 34, wherein the means for holding the components is a spring (74)and wherein the spring (74) is guided force-controlled onto the mountingpins (70) with the interaction of clamp disks (76) which fix the spring(74) in its end position.